The present invention pertains generally to the treatment of urinary incontinence and more particularly to an incontinent bladder control method and apparatus incorporating a prosthesis for selectively restricting urine flow in a urethra.
Both males and females have an external sphincter formed about the urethra which, when functioning normally, constricts the urethra and prevents flow of urine from the bladder except when the bladder is voided during normal urination.
Urinary incontinence may result from several causes. For example, in females stretching or lengthening of the pelvic attachments to the bladder and urethra (termed cystocele and urethrocele) may occur, such as following a normal vaginal parturition, thereby allowing the bladder to descend from a normal position (FIG. 1) into a lower position (FIG. 2) thus functionally shortening the urethra. This form of incontinence may be surgically corrected by re-securing the bladder and urethra into a normal or near-normal position in the pelvis (FIG. 3), thereby regaining normal or additional urethral length. In this type of incontinence, the essential elements of the sphincter are intact.
A more difficult form of urinary incontinence relates to iatrogenic injury to the urethral sphincter. Such injury is common in the male following certain types of prostate surgery (e.g., for prostate malignancy and sometimes for benign prostatic hypertrophy) and produces incontinence as result of damage to or loss of the external urethral sphincter. This form of incontinence is treated by repair or augmentation of the sphincter, or by substitution of its function by implantation of a prosthetic sphincter. It is not treatable by repositioning surgery, as in the case of female urethrocele/cystocele, because that surgery requires an intact sphincter.
There are numerous prior art prosthetic sphincters for selectively closing and opening the urethra to prevent incontinence. These devices typically incorporate an inflatable cuff which surrounds the urethra or encloses it on two sides, and which is inflated to restrict urine flow in the urethra. Examples of such prosthetic sphincters are seen in U.S. Pat. No. 4,571,749 to Fischell, U.S. Pat. No. 4,222,377 to Burton and in other prior patents referenced in applicant's prior patents.
Implementing this approach can encounter surgical difficulties and using it involves problems of control, both with potentially serious complications. Surgery in the female requires a difficult dissection behind the bladder neck and urethra, risking perforation of the adjacent vaginal wall. In males, dissection in this area encounters the prostate and rectum, risking rectal injury/fistula.
After implantation, control and maintenance of pressure in the cuff has been found to be difficult. Inadequate pressure (inflation) applied by such prior art devices may fail to occlude the urethra and thus permit continued incontinence. When sufficient pressure is applied, incontinence can be initially prevented but then may recur as result of partial tissue loss or necrosis of the urethra due to excessive localized pressure applied to the urethra by the prosthetic sphincter.
U.S. Pat. No. 4,846,784 to Haber discloses a manually adjustable sphincteric system, which is inserted as a unit periurethrally in the male via a trocar. In operation, inflation of a balloon located adjacent the bulbar urethra increases local tissue density in the area of the proximal corpus spongiosum. This approach is limited to use in the male.
Another drawback associated with the prior art prosthetic sphincters, which are activated by transfer of an incompressible fluid, relates to the complex control systems used for inflating and deflating the sphincter. Examples of such prior art systems are seen in U.S. Pat. No. 4,571,749 to Fischell and in U.S. Pat. No. 3,744,063, which includes a fluidic control system for inflating and deflating an artificial sphincter that includes four check valves. U.S. Pat. No. 4,846,784 to Haber uses a simpler form of releasable check valve, but discloses no way to control intra-system fluid pressures without further surgery. Other examples are cited in applicant's prior patents.
The disadvantages of implantable prosthetic devices can, in many instances, outweight their advantages. Infections associated with implanted foreign materials require removal with resultant scar tissue which usually precludes repeat surgery (implantation) at that site. Infections most commonly occur when other problems concerning complex prosthetic devices require secondary surgery. Examples of this situation include replacement of defective component parts, leakage of fluid from hydrologically actuated devices, and tissue erosion associated with inflatable prosthetics. The currently available artificial urinary sphincter demonstrates all of the above disadvantages. These have lead to a failure rate ranging from 5-10% and infection rate of about 5%.
These problems prompted development of a simplified prosthesis and method of controlling incontinence as disclosed in applicant's U.S. Pat. No. 4,969,474 and U.S. Pat. No. 5,012,822. These are effective to minimize the above complications and to improve treatment of severe urinary incontinence. The device incorporates fluid transfer between multiple (2) components of a self-contained fully implantable device. As originally conceived, the device is intended to be surgically implanted as a unit with percutaneous access for patients who can manually operate the voiding feature of the device. A fully implantable device avoids external contamination following surgery. The main disadvantage of this approach, as in other systems, is the need for major surgery to perform the implantation. A further disadvantage is the need for secondary surgery for failure of any component or tissue change (erosion) which in prior and current designs can produce loss of function (recurrent incontinence). Repeated or extensive surgery is associated with excessive scar formation which, in turn, reduces blood supply to the area of the prosthesis. High infection rates are directly related to diminished blood supply.
A need, therefore, remains for a way to implant a urinary incontinence device which reduces the extent of surgery and the likelihood of subsequent surgical revisions.